Deciphering the Role of Macrophages in RSV Infection and Disease

Respiratory syncytial virus (RSV) is a major cause of severe respiratory infections in infants, the elderly, and immunocompromised persons. Innate immune responses to RSV, which are crucial for containment of the infection yet may also be linked to severe disease, are well-studied in the main RSV target cells, respiratory epithelial cells, but the role of pulmonary macrophages (MΦs), key innate immune regulators, remains incompletely defined. This review addresses the interaction of RSV with MΦ, discussing the susceptibility of these cells to productive infection, and MΦ responses to RSV, including cytokine and chemokine release and inflammasome activation. Furthermore, factors contributing to variability in MΦ infectivity and responses, such as MΦ polarization, age, differences in RSV isolates, co-infections, and prior innate priming, are presented. Finally, the review highlights discrepancies observed across experimental models, MΦ origins, and RSV isolates used, complicating the interpretation of MΦ-RSV interactions, thereby underscoring the need for standardized methodologies.